This invention relates to a screen guard for protecting a heat exchanger and, more particularly, to an easily removable and cleanable screen guard for a fin-coil heat exchanger to capture cottonwood seed.
Fin-coil heat exchangers are commonly used in split system air conditioners, heat pumps, refrigeration systems, and the like. These devices frequently use a fan to force air to flow over fin coils. The fin coils of these heat exchangers are thin, closely spaced flanges of metal over which air travels to carry heat away from the flanges and hence the heat exchanger. A primary reason for the failure of fin-coil heat exchangers and their components is obstruction of air flow through the fin coils.
While small debris such as dust and dirt can pass through the fin coils, large debris can obstruct air flow through the fin coils. Cottonwood seeds in particular present a significant problem. Cottonwood trees release seeds which open to expose a tuft of fibrous material with many strands extending from the husk of the seed. As an air conditioner operates, it draws air and cottonwood seeds into the heat exchanger. Fibers of the cottonwood seeds become entangled in the thin, closely spaced fin coils of the heat exchanger and eventually impede air flow through the coils. Even more significantly, fibers of cottonwood seeds bridge the narrow openings between fin coils to create a filter media which collects dust and dirt that would normally pass between the fin coils. Dust and dirt accumulate on the filter media formed by cottonwood seeds further impeding air flow and ultimately plugging the narrow openings between the fin coils. Thus, cottonwood seeds impede air flow eventually causing the heat exchanger to fail requiring expensive repair or replacement.
Once cottonwood seeds are caught in the fin coils, they are not easily removed. Spraying the fin coils with water to remove cottonwood seeds is time consuming and generally fails in removing cottonwood seeds. Further, the undesirable tendency of cottonwood seed tufts to collect dust and dirt is intensified by moisture. Physically removing the cottonwood seeds with a wire brush, for example, is an even more time consuming task and can damage the fin coils.
U.S. Pat. Nos. 5,156,662 to Downing et al and 4,961,849 to Hull et al disclose filtering assemblies utilizing standard furnace filter material and spun glass/fiber glass screen respectively. While the Hull reference purportedly proposes a filter for any application, the Downing reference proposes an exterior filter system to cover a housing of an air conditioning system to prevent dirt and debris from passing through to the heat exchanger. However, these filters, which are capable of filtering dust and dirt, significantly reduce air flow through the heat exchanger, and reduced air flow degrades the efficiency of the air conditioning system. To compensate, the fan speed is increased thereby increasing power consumption and operating cost. As the filter becomes clogged with dust, dirt, and cottonwood seeds the air flow through the heat exchanger is further reduced thereby degrading efficiency. Therefore, simply providing a filter for the heat exchanger does not provide a satisfactory solution to the cottonwood seed problem outlined above.
The Downing reference proposes attaching the filter to the air conditioning unit with a group of straps and rings which are attached to the perimeter of the filter. While the straps and rings function to satisfactorily attach the filter, it is somewhat time consuming to thread each strap through a corresponding ring to attach the filter, and thus, the filter assembly of Downing discourages removing the filter for cleaning or replacement. Further, the straps and rings limit the versatility of the filter requiring different length straps that are positioned in different locations around the perimeter of the filter for different air conditioners, and attaching the straps and rings also complicates and increases the cost of manufacturing the filter.
The Hull reference attaches a filter to an intake air vent of a car with a magnetic frame that is connected to the perimeter of the filter. Thus, the Hull reference provides a filter that is quickly and easily attached and reattached when ferrous metal is available for the magnetic frame to attach to. However, the use of non metallic materials and nonferrous metals is increasing, and the Hull reference does not provide a solution for convenient attachment to such materials. Further, the Hull reference does not specifically address how filters can be attached to heat exchangers.
Thus, preventing the accumulation of cottonwood seed and similar filter forming debris on fin coils of a heat exchanger and maintaining a high air flow rate through the heat exchanger are desirable to extend the life and enhance the efficiency of the heat exchanger. Further, providing a simply manufactured and versatile cleanable screen guard with quick and easy means for attachment to any material is desirable to reduce manufacturing cost, increase the rate of manufacture, encourage frequent cleaning, and reduce the time spent detaching and reattaching the screen guard for cleaning.